emm 就是这么写吧大概。。官网 tutorial 改了改

```
class User(Base):
id = Column(Integer, primary_key=True)


class UserAddress(Base):
id = Column(Integer, primary_key=True)
user_id = Column(Integer)
address_id = Column(Integer)

user = relationship("User", primaryjoin="foreign(UserAddress.user_id) == User.id")
address = relationship("Address", primaryjoin="foreign(UserAddress.address_id) == Address.id")


class Address(Base):
id = Column(Integer, primary_key=True)
```